Sift the flour, baking powder, baking soda and salt, if using. Set aside.
Preheat the oven to 175 C and grease a 9x5 loaf tin. You can also line it with greased baking paper for easy removal.
Mix the milk and lemon juice in a small bowl and set aside to sour.
In a mixing bowl, beat the butter and sugar with a hand mixer on medium speed till pale and fluffy. Add the eggs and vanilla and beat well.
Now add the orange juice and zest and beat to combine.
Finally beat in the soured milk and flour mixture alternately, starting and ending with the flour so that the batter stabilises. If it still curdles a little, it's ok. It will smoothen out once all the flour is mixed in.
Spoon the batter into the prepared loaf tin, smoothen the top and bake for 35 to 40 minutes or until a toothpick poked in the center comes out clean. Cover the top with foil to prevent it from getting burnt if it's browning too fast and rotate the tin halfway through the baking time to ensure even browning.
Set the cake aside to cool for about 1 hour. Remove from the pan and set on a tray to catch the drips from the glaze.
To make the glaze, combine all the ingredients in a small saucepan and set on low heat, stirring constantly. Let the butter melt and the glaze start to simmer and appear frothy, then take it off the heat and immediately pour all over the cake.
Let the glaze set for about 10 minutes, then slice thickly and dive in!